Field of the Invention
The invention relates to substantially amorphous or microcrystalline Al-based alloys.
There are many alloys in an amorphous state, which are produced by rapid cooling at a rate which is generally higher than 10.sup.5 .degree. C./sec from a random state (liquid or vapor). In particular, alloys of type T.sub.i X.sub.j are known, in which T represents one or more transition metals (in particular iron) and X represents one or more metalloids (non-metalloids) such as B, P, Si, C, Al, with i.gtoreq.50 atom %. In such alloys, Al occurs as a minor element, the proportion of which, generally of the order of 10 atom %, does not exceed 35 atom %.
For Al-based alloys (containing more than 50 atom % Al), the technical literature reports on attempts to produce amorphous alloys, which were carried out in relation to binary alloys containing Bi, Cd, Cu, Ge, In, Mg, Ni, Pd, Si, Cr, Ag or Zn, but only four of them, Al-Ge, Al-Pd, Al-Ni, Al-Cr were found to be very locally amorphous (regions which are visible in electron microscopy), and that occurs with very high rates of cooling of the order of 10.sup.9 to 10.sup.10 K/sec, which are very difficult to attain on an industrial scale: see T. R. Anantharaman et al. "Rapidly Quenched Metals III", volume 1, Editor B. Cantor, The Metals Society, London (1978) page 126 and P. Furrer and Warlimont, Mat. Science and Eng., 28 (1977) page 127.
With regard to ternary alloys, amorphous alloys were produced by A. Inoue et al., (Journal of Mat. Science 16, 1981, page 1895) but they relate to the systems (Fe, Co, Ni)-AL-B, which may contain up to 60 atom % Al and generally from 15 to 45-50 atom % B.